This invention relates to a process for the preparation of cyano-substituted cyclopropane derivatives, referred to herein generally as cyclopropanecarbonitriles, which can readily be converted by known methods into their corresponding cyclopropane carboxylic acids. Such carboxylic acids, for example, 2-(2,2-dihalovinyl)-3,3-dialkylcyclopropanecarboxylic acids and their corresponding alkyl esters are key intermediates in the manufacture of a group of compounds known as "synthetic pyrethoids" which exhibit remarkable levels of insecticidal and acaricidal activity. United Kingdom Pat. No. 1,413,491 discloses and claims an important group of these synthetic pyrethoids and also demonstrates the difficulties in synthesizing the cyclopropane carboxylic acid precursors thereof.
The compounds produced by the process of this invention are valuable intermediates in the preparation of that class of carboxylic acids which in turn are used to produce insecticidally active compounds such as, for example, the alphacyano 3-phenoxybenzyl ester of 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropanecarboxylic acid as disclosed in example 20 of the United Kingdom Pat. No. 1,413,491.